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Empty Trash won't work

Badness level, on a scale of 1 (not bad) - 100 (WTF?): 5

If you delete files on a ZFS volume via the Finder, you won't be able to use Empty Trash properly. The files don't show up in the Finder anymore, but they're actually just moved to a hidden directory called ".Trashes". You have to use "rm" in the Terminal to really remove the file (or just "rm -rf .Trashes").

As far as most things go, this is not a huge deal, but you could easily forget that this issue exists and accidentally let your zpool fill up over time and then waste a bunch of time troubleshooting it. Maybe some sort of Applescript/Automator/cronjob approach would provide a semi-seamless workaround.